Generator buying for Dummies

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9 years 11 months ago #32424 by Valmai
It is time and I can now afford to considerbuying a generator, I've tried reading up on the subject but it is all as clear as mud to me.
I want to have at least 2/3 lights
The ablity to run my freezer, even if only for a couple of hours a day to keep it cold.
TV to know what is happening around the country
Submersible pump for stock water and pressure pump for running water in the house.
1 or 2 power points and the stove.
I understand I may need to stagger the use of things which draw a lot of power.
It needs to be reasonably portable.
So,diesel or petrol? How do I work out how much wattage I need? How much extra wattage should I have to 'future proof' it?
What questions have I not asked that I should have?

Carbon-based biological unit.

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9 years 11 months ago #433101 by GrantK
Replied by GrantK on topic Generator buying for Dummies
If you want to run your electric stove from a generator, you will need to buy a humungous one!!! Probably at least 6kW.

If you are prepared to cook with Gas or on top of a Wood Burner on rare occasions when the power is out, it will save you an awful lot of money.

It is also not a good idea to buy a very large generator and only run it with a very light load for most of its life, especially if it's a diesel. Your requirement for "reasonably portable" also rules out a 6kVA generator, as they are very heavy and need two people to lift.

I would go for a 2 to 3kVA petrol unit, which are not too heavy and much quieter than a diesel. Also much better for occasional use than a diesel, which really like to be run close to capacity for a good while.

We have an old Yamaha 2.5kVA generator which we bought second-hand many years ago. It still starts after one or two pulls, even if it hasn't been used for months. I would recommend looking around for an older Honda, Yamaha, Robin or other Japanese brand in preference to buying a brand-new Chinese unit for a similar price.

I think you will be disappointed at the reliability and voltage regulation of the no-name Chinese Generators. We have that type of engine on a waterblaster, and it goes really well for quite a while, but eventually overheats. Whereas the Honda on my sprayer will run for hours and hours without missing a beat.

Our old 2.5kVA generator will run all the appliances in our house except for the stove. It also struggles a bit with the microwave, but will work at a pinch. Computers, Printers, TVs, Pumps, Vacuum Cleaners and Lights are no problem. Just add up all the wattages of the appliances you want to run together, by looking on the label for each. And then add another 500 Watts for good measure!

Live weather data and High/Low records for our farm at: www.keymer.name/weather

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9 years 11 months ago #433133 by igor
Replied by igor on topic Generator buying for Dummies
The first question that springs to my mind is whether you will be using the generator all the time or only as a back-up supply when mains electricity is not available. If it is only an emergency back-up how about something that runs off the pto of your tractor?

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9 years 11 months ago #433141 by Hawkspur
I agree with the comment about diesels not liking to be run at low load for too long. Because our setup is being staged, and we can't fork out for the solar panels yet, we have a diesel generator that has to do the trickle charge. So OH has set up an ingenious custom monitoring electronic thingummy, that switches on additional loads at intervals. :D

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9 years 11 months ago #433163 by griev
Replied by griev on topic Generator buying for Dummies
yes indeed stay well away from the made in China ones, Some Diesels don't care what you put on, our old one was 3 phase and ticking over you could dump whatever you wanted on it and it didn't care less, the new diesels are less tolerant, and are designed to be operated at a spec level for a long time,

We are on gas for cooking and recommend prob getting a petrol 3.5-4kw one, 2.5kw with the fridge and the TV might cause some issues esp if you wanted to plug something else in,

however it is easy to figure out your requirement, all elect items have a wattage req, so figure out what all the max wattage will me at one particular time add in an extra 20% for incidentals and pick a generator a little bigger than that, most decent generators will handle short surges from motors start up current draw.

Certainly I am currently looking at replacing the Chinese one we are using while I fix the big beast with a Honda, they do have a great reputation and seem to be the most economical to boot.

Let the sun shine on my solar panels[:)]

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9 years 11 months ago #433203 by Blueberry
we bought a generator several years ago, because we lose power quite regularly, and most often on a Saturday, just when i have 40 - 50 loaves of bread ready for baking....[:(!]

Anyhow, hubby calculated we'd need enough juice to run several (up to 5, depending on season) freezers (and they use quite a bit when starting up, as opposed to once running!), the water pump, the water filter, light and power for the 115L baking oven.

we 'stumbled' upon an earlybird special at Goldpine, 8kW, petrol, it's about the size of a 110L storage box on wheels, with handles, and it cost us just under one Grand. has three plugs, and is a Godsend.

we see similar models every now and again, and they are all around the $2K - $3K.

Valmai, what i'm saying is; once you have determined your requirements, shop around.

[;)] Blueberry
treading lightly on mother earth

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9 years 11 months ago #433394 by spark
Replied by spark on topic Generator buying for Dummies
Hi,

I imagine that your lights and TV will spend many hours a day running, but only at a low rate of power consumtion (eg 3x 20W fluorescent lamps, 30W for a laptop and 100W for the LCD TV, etc), and that your high-draw appliances (water pump, etc) will only need to run flat out for a longer period of time (eg to pump water up the hill to your tank which gavity feeds the taps in your home).
If this is the case, you might want to consider buying an "inverter charger" and a bank of rechargable deep-cycle batteries - when the generator is not running, your small loads will run from battery power via the inverter, and when the generator is running (because you want to run the water pump, etc), the batteries will be recharged automatically.

If you have the money to spend, you can buy an inverter charger big enough to run the water pump, along with an electric start generator and unit that automatically starts the generator if the batteries are getting low, and then stops the generator once the batteries are charged (this sort of system also lends itself to the addition of solar or wind generation).

You can also do this on the cheap - get a high rate battery charger and plug it into the 230V output from the generator, connect it to a set of deep cycle batteries (probably 12 or 24V - easy to get lights and appliances) and connect the batteries to some DC lights and a TV that runs from DC (or a cheap inverter to make enough 230V to run the TV from the batteries - most flat panel LCD TVs have modest power demands).

Either the cheap or the expensive system will mean that you do not have to have your generator running "all the time" just to make the lights or TV work.

Induction motors (that means your water pump, the compressor in your fridge, etc) draw a big surge of current when they start - a rule of thumb is that your generator should be at least twice as big as the largest induction motor that you will use it with. (eg if you have a 1.5kW/2hp water pump then you will want a 3kVA or larger generator).

Diesel engines do not like prolonged operation at low load - it causes "wet stacking" (a thick oily, tar like build up in the exhaust system) and "glazed cylinders" (a buildup of carbon inside the cylinder). You can avoid these problems by following the engine manufacturer's directions - this usually means making sure that your diesel runs at no less than about 1/3 of it's rated capacity. Or alternately, if it is run at less than 1/3 of rated capacity, it needs to be periodically run into a "load bank" (50 to 100% of rated capacity) to ensure that it gets hot enough to burn any c#%p out of the engine and exhaust. An electric hot water cyclinder heater and or electric heaters (placed inside if you want heat!) are an easy way to implement a load bank on the cheap.

Any generator does not like operating for short periods of time on a regular basis, eg starting the generator, running for 3 minutes to heat food in a microwave and then shutting the generator down, as the engine fails to reach proper operating temperature, which can result in water (steam is a byproduct of burning fuel) condensing inside the motor and exhaust where it can cause corrosion. Diesel engines asside, you can also carbon up the cylinder and foul the spark plugs of a petrol engine if it never gets hot enough to come off of the automatic choke.

"Prime power" generators generally run at 1500rpm - they are bigger, heavier, more expensive, but they generally don't make as much noise and if maintained properly, have a long useful life.

"Standby power" generators (most cheap portable generators) generally run at 3000rpm - they are smaller, lighter, cheaper, but they are noisier and have a shorter life.

Inverter generators (available in both petrol and diesel) vary the engine speed to match the demand for electricity, and use a fancy electronic device (the inverter) to ensure that your appliances see nice steady 230V 50 Hz AC power even as the speed of the generator varies. When they work, they work well, and a big advantage of these units is the reduced fuel consumption, reduced noise and reduced engine wear. However, if the inverter breaks (more likely on a cheap & nasty inverter generator) then you won't have any power even though the motor may still start and run.

Some cheap petrol generators have "side valve" engines (like the traditional Briggs & Stratton lawn mower engine) - they are cheaper to manufacture than overhead valve engines, but due to the lower compression ratio (and resulting loss of thermal efficiency) they use significantly more fuel than an equivalent sized generator with an overhead valve engine.

Cheers

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9 years 11 months ago #433401 by Valmai
Replied by Valmai on topic Generator buying for Dummies
Thanks everyone for your comments. Sparks, I'm going to have to re-read your post a few times:confused:.
With my set-up I would only have to run the submersible pump to top up the storage tank if needed. The pressure pump for the house supply comes on when ever I turn any tap on so needs power permanently. This pressure pump also pumps water to the stock troughs. I would expect that I could unplug the freezer and then plug it in and run it for a couple of hours just to keep everything frozen. I could get by with only using hot plates and not the oven, would this make any difference?
When I do get this generator, do I get an electrician to put a plug into the meter box for it, or is it connected some other way?

Carbon-based biological unit.

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9 years 11 months ago #433404 by GrantK
Replied by GrantK on topic Generator buying for Dummies
Valmai, there's someting I'm not getting here:

One minute you're talking about pumps needing power permanently...

Valmai;431963 wrote: With my set-up I would only have to run the submersible pump to top up the storage tank if needed. The pressure pump for the house supply comes on when ever I turn any tap on so needs power permanently. This pressure pump also pumps water to the stock troughs. I would expect that I could unplug the freezer and then plug it in and run it for a couple of hours just to keep everything frozen.

Then you talk about electricians and meter boxes, so it seems clear that you already have mains power and are intending to keep it that way...

Valmai;431963 wrote: When I do get this generator, do I get an electrician to put a plug into the meter box for it, or is it connected some other way?

And then you talk about cooking on hot plates...

Valmai;431963 wrote: I could get by with only using hot plates and not the oven, would this make any difference?

Others above have assumed you are talking about living off-grid, but to me it doesn't sound that way. How long are these expected power outages you are trying to cover?

Cooking on hot plates is still an enormous power drain for any generator. It will need to be very large in order to cope. Much better ideas are:

1) Have a gas barbeque in a shed for the odd occasion power is out when you need to cook.

2) Make do with a microwave.

Either option will save you a tremendous amount of money compared to buying a generator which is grunty enough to power hotplates.

We have a neighbour who tried it with his $100k+ off-grid power system. It didn't work, and he had to go back on the grid, with his tail between his legs.

Live weather data and High/Low records for our farm at: www.keymer.name/weather

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9 years 11 months ago #433411 by spark
Replied by spark on topic Generator buying for Dummies

Valmai;431963 wrote: When I do get this generator, do I get an electrician to put a plug into the meter box for it, or is it connected some other way?

If the generator has ordinary 3 pin sockets on it, then you can just plug in an extension lead with your appliances on the other end of it (usual electrical safety rules about extension leads and multi-boxes apply).

Alternately, you get a sparky in, and get them to change the main switch on your meter box for a three position "mainsoffgenerator" switch and install a weatherproof socket inlet (the same type that you find on the side of a caravan) outside for the generator to plug into. You sparky will also be able to make you up a lead that plugs into the generator and the outdoor socket inlet. If you buy a "fixed-wired" generator (no socket outlets on it) then you will definitely need a sparky.

A single hot plate will have a peak demand of somewhere from about 1.5kW to 3kW of electricity - you don't need a huge generator to run ONE hot plate at a time, but if you want to run several at the same time, plus other appliances?, then the electricity demand starts to add up and you will need a big expensive generator to make everything work.

A standard 16 amp caravan type socket inlet can handle up to a 3.6kVA generator - if you buy a 3kVA or larger generator, you should have no trouble running one big hotplate (or maybe two small ones at the same time).

GrantK is right regarding hotplates and battery power systems - they will run your batteries flat in a very short time. Gas or firewood is cheaper than the big generators, big batteries and big inverters required to support electric cooking.

Cheers

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9 years 11 months ago #433502 by Valmai
Replied by Valmai on topic Generator buying for Dummies
Sorry for the confusion I should tell you that all I know about electricity is how to turn the switch on and that exposed wires bite! I'm wanting a generator for those times we have a power cut. Surely using a petrol/deisel generator to go off-grid would be rediculously expensive. If using the oven or stove top(hotplates) is too much I do have a bbq. I thought that to replace mains power with a generator (during a power cut) you needed to have the geney plugged into the mains meter box. Is there another/better way to do it?
As for the pumps, I have a submersible pump which fills up a 25000 ltr tank. The pressure pump pulls water from this tank to supply the house. So the submersible would only be needed if the 25k ltr tank is empty, but the pressure pump would need to operate regularly every time I turn a tap on.

Carbon-based biological unit.

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9 years 11 months ago #433507 by GrantK
Replied by GrantK on topic Generator buying for Dummies

Valmai;432072 wrote: If using the oven or stove top(hotplates) is too much I do have a bbq.

To cover the occasional power cut, that will be by far your cheapest option.

Valmai;432072 wrote: I thought that to replace mains power with a generator (during a power cut) you needed to have the geney plugged into the mains meter box. Is there another/better way to do it?

Spark has suggested the "proper" way to do it above, by using a 3-position switch.

However, for just the occasional power cut, we find it satisfactory to run a long extension lead across the lawn from a small shed near our house where we have the generator. You need somewhere with good ventilation and not right outside your window or else the noise will be a nuisance.

So this is what we do:
- Start the generator, but leave the circuit breaker turned off.

- Plug in the extension lead and run it across the lawn (make sure it's a long one so there are no connectors exposed to the rain).

- Unplug everything you want to keep going from the normal wall sockets and connect them to a multi-socket power strip.

- Plug the long extension lead from the generator into the power strip.

- Go outside and turn on the circuit breaker on the generator.

That's it, you are up and running. Reverse the procedure when the power comes back.

Live weather data and High/Low records for our farm at: www.keymer.name/weather

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9 years 10 months ago #433607 by wandering free
We just use a 5.5hp Honda 2.5kVA generator and do like GrantK does with extension leads, it is much the simplest way and then we have a small gas cooker similar to the ones used on boats.

What's good about the smaller generators is there potability, we cart ours around and have an electric chain saw and pole saw and use them for all our tree felling and pruning, they are so much more convenient than petrol.

I would think it would cost a few hundred dollars to wire up and get electrically certified an isolation switching box to allow you to plug into the mains supply, any mistakes and you could fry the repair man half a mile down the road up a pole fixing the fault.

Just me and the cat now, on 2 acres of fruit and veg + hazel nuts, macadamia, chestnuts and walnuts,
www.youtube.com/user/bandjsellars?feature=mhee

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9 years 10 months ago #433612 by Mich
Replied by Mich on topic Generator buying for Dummies
Hi Valmai - I don't think you'll ever regret getting a generator. There's something very comforting knowing that (particularly on crappy winter nights) you'll always have power, and in the event of a disaster when power might not be restored for days, it will be a god-send. We consider ours one of the best purchases we've made.

We have our petrol one wired up to the house with the 3 switches that Spark was talking about, along with a small capacity meter and buzzer that tells you when the power comes back on again. Ours is grunty enough to run pretty much everything except the stove and we really only have to check the load if we wanted to run something that generates a bit more heat at the same time as the normal stuff is running (e.g. hair dryer or electric jug).

We were advised to start up the generator regularly (DH does it at least once a month) and run it for about 10 minutes or so to keep everything in good working order for when you need it. Another recommendation is to make sure your generator fuel is rotated so you always have a reasonably fresh supply.

Cheers, Mich.

Good exercise for the heart is to bend down and help someone up. Anon.

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9 years 10 months ago #433677 by cj4a
Replied by cj4a on topic Generator buying for Dummies
like mich I have a change over switch in the main's box and wire up in my garage with a caravan plug and have only run my genny once with a 1500 watt heater to make sure it went, it's only a cheap 2.5kw? on from miter 10 but only plan on useing it for power cuts for light and the fridge
good luck with your genny purchase

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